1. Field of the Invention
This invention relates to the fuel tank of an automobile, and more particularly to a fuel leakage prevention apparatus for preventing liquid fuel leakage from the fuel tank to an evaporation pipe for discharging evaporated fuel to a canister.
2. Description of the Prior Art
Generally, the fuel supplying system of a gasoline engine comprises a fuel tank, a canister, a carburetor, etc.
A fuel tank 1 is an apparatus for storing and supplying liquid fuel to carburetor 8 and the fuel tank 1 includes a gassing-up gate 2, a feeding pipe 3 for supplying the stored fuel to carburetor 8, a reserver 5 installed at the top of a elevation pipe 4a for storing liquified fuel connected with an evaporation pipe 4 for discharging evaporated fuel to a canister 7 and a return pipe 6 for returning the liquified fuel at the reserver 5 to the tank 1.
The fuel stored in the fuel tank 1 is supplied to the carburetor 8 by a fuel pump (not shown) and is mixed with air in the carburetor 8. The mixture is supplied to cylinders 9 of the engine for combustion.
Meanwhile, exhaust gas of automobile includes harmful gases such as carbon monooxide CO, hydrocarbon HC, nitrogen oxides NOx. Especially, hydrocarbon is continuously generated at the fuel tank 1 and at the carburetor 8. The hydrogen carbon rises up through the elevation pipe 4a and passes the evaporation pipe 4 and is accumulated and stored at the canister 7 by being absorbed in activated carbons encased therein upon stopping and parking a car, and then is supplied for combustion to the carburetor 8 upon travelling.
Further, a fuel leakage prevention apparatus, which also functions as a discharging valve for venting the evaporated fuel generated in the fuel tank 1, is installed at the elevation pipe 4a or at the top of the fuel tank 1 connected with the elevation pipe 4a. Therefore, when a car is shaking, is gassing up, is turning around or is overturned, the fuel leakage prevention apparatus prevents the liquid fuel of fuel tank 1 from flowing into the evaporation pipe 4 and accumulating in the canister 7 which would cause a decline in the functionality of the canister 7 or allow hydrocarbons to diffuse to the atmosphere.
FIG. 2 shows a prior fuel leakage prevention apparatus.
As shown, the prior fuel leakage prevention apparatus is installed at the top of the fuel tank 1 connected with the evaporation pipe 4. The fuel leakage prevention apparatus comprises a cylindrical body 10 having a plurality of vent holes 11 and 12, a ball of heavy weight 13 located at the bottom of the body 10, a base plate 14 located on the ball 13, a coil spring 15 on the base 14, a float 16 located at the top of the coil spring and suspended upward. Meanwhile, a neck 18 shaped like a venturi pipe is formed at the top of the body 10. And a sealing surface 17 is formed for shutting off leakage of liquid fuel from the fuel tank 1 at the bottom surface of the neck 18 which contacts the float 16.
Therefore, the evaporated fuel generated in the fuel tank 1 passes the holes 11 and 12 of the body 10 and rises up to the evaporation pipe 4 through a gap between the float 16 and the body 10. And the evaporated fuel enters into evaporation pipe 4 and accumulates in the canister 7.
However, the float 16 can shake on the base 14 if the fuel in the fuel tank 1 shakes upon gassing up a car and upon travelling of a car since the gap between the body 10 and the float 16 have a considerable space for a gas passage.
For example, sealing between the float 16 and the sealing surface 17 becomes opened partially by shaking the fuel surface upon gassing up a car.
Therefore, there is a problem in the conventional fuel leakage prevention apparatus, in that when liquid fuel flows into the gap between the body 10 and the float 16 by shaking of the fuel, the apparatus could not shut off such fuel leakage so that the liquid fuel leaks from the apparatus and flows into the canister 7 along the evaporation pipe 4.
Further, when the car turns, the float 16 tilts in the body 10 thereby opening the sealing partially, and such opening also causes the fuel leakage.
Thus leaked fuel fills the canister and hinders the canister absorption of hydrocarbon, so hydrocarbon diffuses to the atmosphere and contributes to air pollution.
Accordingly, it is an object of the present invention to provide a fuel leakage prevention apparatus for effectively shutting off leakage of liquid fuel as well as allowing easy discharge of evaporated fuel.